Radio frequency (RF) systems often exhibit frequency-dependent gain slope and ripple in their spectral responses. This non-uniform frequency response is inherent to all electronic components. However, other factors can exacerbate the frequency response. For example, these include impedance mismatch, frequency dependent RF components and environmental effects.
Ripple and gain slope ultimately cause errors in data transmission. As a result, a gain flatness metric is often specified for RF systems. By way of example, a gain flatness of +/− 1 dB may be required for frequencies in a 500 MHz bandwidth centered at 10 GHz.
Accordingly, various equalization techniques are often implemented to flatten the frequency response. Typical analog electronic equalizers are static and generally provide an inverse gain slope to what the frequency response of the system is. However, some implementations use dynamic analog electronic equalizers, which are active systems designed to correct voltage standing wave ratio (VSWR) as well as gain slope.
One example equalizer is set forth in U.S. Pat. No. 7,394,331 to Yeung et al., which discloses a programmable passive equalizer. The equalizer is programmable to respond to one or more changes in a signal caused by the communication of the signal through various signal components. The passive equalizer includes a programmable resistor device and a programmable capacitor device arranged in parallel to one another, with the programmable resistor device and the programmable capacitor being arranged to provide an output to a node. An inductor device and a resistor device are arranged in series, with the inductor device and the resistor device also being configured to provide an output to the node.
Generally speaking, electronic equalizer approaches may suffer from various drawbacks. These may include added loss into the system, narrowband response, low resolution, and poor performance at high frequencies. As such, further enhancements may be desirable for RF signal equalization in various applications.